Which antivirus for a noob?

Hi,
I have a small sister & want to give my old Computer to her. Now i want to install a good antivirus on the machine so that it will automatically update it & will secure the system. What is the best antivirus for this purpose?

I use AVG, but I honestly can't remember the last time it ever found any malware on my system. I think the best antivirus system is smarter computing. Don't do stupid things and stupid things won't happen to you.

Here you will find out the best antivirus

Six years ago I gave my mom a computer—and she barely knew how to use the mouse. It ran Symantec antivirus, was configured to automatically install Windows and other updates and her account did not have administrative rights. Fast forward to today and while she is on her third computer, the same principles have been applied and she has never had any kind of malware on her computers.

If I were to do it again today I would go with Kaspersky 9, set it all to max and set it to update every hour. I would take KAV over NOD32 anyday especially what NOD32 has been letting through lately on my test machine but that choice is just a personal opinion.
Make sure to set any and all Anti-malware devices to autoclean.